In many widely used packet-oriented communications networks, for example in the Internet, no Qualities of Service are guaranteed for connections between terminals in these communications networks unless additional precautions are taken. The Quality of Service (QoS) of a connection may cover various transmission and connection parameters, such as the transmission bandwidth, the transmission speed, the permissible error rate and/or the transmission duration.
In present-day communications systems, which are frequently based on such packet-oriented communications networks, so-called resource managers are provided in order to ensure a predetermined Quality of Service. These resource managers are in each case associated with a communications network or a network element, and administer their respective transmission resources. A resource manager may in each case reserve transmission resources, which can be predetermined, on a connection-specific basis for connections which are to be set up. Once transmission resources have been successfully reserved, the resource manager then monitors the permanent availability of the reserved transmission resources for the respective connection.
In many cases, the start point and end point of a connection are not in the same communications network or network element, so that the connection has to pass via a plurality of communications networks. In order to reserve predetermined transmission resources for such a connection, these resources must be reserved separately in each individual communications network or network element that is involved in the connection.
According to known methods, this is done by transmitting a reservation request to the resource manager for that communications network which is closest to the connection destination on the route. This resource manager attempts to make an appropriate resource reservation in its communications network and, if successful, transmits the reservation request further to that resource manager which is responsible for the next communications network on the connection route. This resource manager carries out the same procedure, and the reservation request is passed on until either a corresponding resource reservation fails in one communications network or until the reservation request reaches the resource manager which is responsible for the destination communications network. If the resource reservation is successful, this last resource manager transmits an acknowledgement message via all the resource managers involved, back to the initiator of the connection in the first communications network. The initiator of the connection then causes the connection to be set up via the individual communications networks. One such method is described, by way of example, in the Internet draft “A Discussion of Bandwidth Broker Requirements for Internet2 Qbone Deployment”, Version 7, R. Neilson, J. Wheeler, F. Reichmeyer, S. Hares (Editors) dated August 1999, http://www.merit.edu/working.groups/i2-qbone-bb/doc/BB Req7.pdf, 10.7.2000, in particular on pages 12 and 13.
In this known method, the process of setting up a connection via a plurality of communications networks is, however, delayed considerably owing to the complex signalling. Particularly in the case of connections via the Internet, which comprises a large number of individual communications networks, this has been found to be highly disadvantageous.